As a method of thinning a semiconductor wafer, there has been known a method in which a semiconductor wafer is bonded to a thick supporting substrate with an adhesive to grind the semiconductor wafer. By bonding a semiconductor wafer to a thick supporting substrate, the flatness of the semiconductor wafer at the time of grinding can be well maintained, and the semiconductor wafer can be uniformly thinned to a thickness of about 15 to about 100 μm. The thinned semiconductor wafer has required processes such as circuit pattern formation performed on a ground surface thereof while remaining bonded to the supporting substrate, and then is separated from the supporting substrate and is subjected to dicing to be formed into chips.
According to the above-described method, it is necessary to separate the semiconductor wafer from the supporting substrate after the thinning. However, the thinned semiconductor wafer of course has a small mechanical strength and is likely to be broken. For this reason, there is required a method capable of separating the semiconductor wafer from the supporting substrate without breaking the semiconductor wafer. On the other hand, the separation work greatly affects the productivity of semiconductor chips, and when time is taken for the work, the productivity decreases. For this reason, there is required a method capable of separating the semiconductor wafer from the supporting substrate for a short period of time.
As described above, the application of the method in which two substrates are bonded together through an adhesive, and then be separated into the respective substrates again is not limited to the above-described case of the semiconductor wafer and the supporting substrate. It is applied widely in various fields, in which, similarly, there is required a method capable of separating the bonded substrates for a short period of time without breaking the substrates.